1. Field of the Invention
This invention relates to a tool-bit holding device in a percussion or impact tool such as an electrically powered hammer.
2. Description of the Related Art
In a known tool-bit holding device in a percussion tool, a ball is provided in a retainer sleeve designed to hold a tool bit. The ball can move between an active position and an inactive position. When assuming the active position, the ball engages the shank of the tool bit so that the tool bit is held in position. When assuming the inactive position, the ball disengages from the shank of the tool bit so that the tool bit can be released. The movement of the ball between the active position and the inactive position is implemented by rotating or axially moving another member provided radially outward of the retainer sleeve. In an alternative design, the ball can be automatically moved between the active position and the inactive position.
Operation of the known tool-bit holding device requires a certain level of load. The known tool-bit holding device can not be easily handled.
There is a known easily-operated tool-bit holding device. The known easily-operated tool-bit holding device is expensive since it is composed of many parts.
In a known mechanism for adjusting the angular position of a tool bit relative to the body of a percussion tool, a steel ball extends into a groove in a retainer sleeve to engage the retainer sleeve. The steel ball can be moved relative to the retainer sleeve along a radial direction. The steel ball is urged by a spring. An adjustment of the angular position of the bit tool can be executed provided that the spring is deformed by an operation grip to allow radial movement of the steel ball.
The known mechanism can not be easily handled since it is necessary to deform the spring by the operation grip during the adjustment of the angular position of the tool bit.
It is a first object of this invention to provide an inexpensive tool-bit holding device in a percussion or impact tool.
It is a second object of this invention to provide an easily-operated tool-bit holding device in a percussion or impact tool.
A first aspect of this invention provides a tool-bit holding device in a percussion tool (an impact tool). The percussion tool includes a piston (25), a striker (21), an intermediate member (17), and means for causing the striker (21) to follow reciprocation of the piston (25) and to strike the intermediate member (17). The tool-bit holding device comprises a rotatable and axially-movable retainer sleeve (4) for accommodating a shank of a tool bit (1); a lock member (7) supported by the retainer sleeve (4) and being movable radially with respect to the retainer sleeve (4); means for engaging the lock member (7) with the shank of the tool bit (1) to limit axial movement of the tool bit (1); a fixed front cover (14) extending radially outward of the retainer sleeve (4); means (13) for urging the retainer sleeve (4) axially forward; a small-diameter surface portion (14b) formed by an inner surface of the front cover (14), and contacting the rock member (7) and projecting at least part of the lock member (7) inward of the retainer sleeve (4) to engage the lock member (7) with the shank of the tool bit (1) when the retainer sleeve (4) is placed at an active position by the urging means (3); and a conic surface portion (14a) formed by the inner surface of the front cover (14) and adjoining the small-diameter surface portion (14b), the conic surface portion (14a) being engageable with the lock member (7) and variably limiting radial movement of the lock member (7) as the retainer sleeve (4) moves axially.
A second aspect of this invention is based on the first aspect thereof, and provides a tool-bit holding device further comprising means for inhibiting the lock member (7) from moving axially relative to the retainer sleeve (4).
A third aspect of this invention is based on the first aspect thereof, and provides a tool-bit holding device wherein the lock member (7) comprises a steel ball (7).
A fourth aspect of this invention is based on the first aspect thereof, and provides a tool-bit holding device further comprising a plurality of grooves (4a) formed in the retainer sleeve (4), an engagement member (12) supported on the front cover (14) and being movable radially with respect to the retainer sleeve (4), the engagement member (12) being fittable into one of the grooves (4a) the retainer sleeve (4), and a holder (10) rotatably provided on the front cover (14) and limiting radial movement of the engagement member (12) depending on a rotational position of the holder (10).
A fifth aspect of this invention is based on the fourth aspect thereof, and provides a tool-bit holding device further comprising a spring (11) for urging the engagement member (12) toward the retainer sleeve (4), the spring (11) having a portion contacting the engagement member (12) and being radially movable, a small-diameter area (10a) formed by an inner surface of the holder (10) and being engageable with the portion of the spring (11) to inhibit radial movement of the portion of the spring (11) and radial movement of the engagement member (12), and a large-diameter area (10b) formed by the inner surface of the holder (10) for allowing radial movement of the portion of the spring (11) and radial movement of the engagement member (12).
A sixth aspect of this invention is based on the fifth aspect thereof, and provides a tool-bit holding device wherein the spring (11) comprises a leaf spring (11) fitting around a portion of an outer circumferential surface of the front cover (14).
A seventh aspect of this invention is based on the sixth aspect thereof, and provides a tool-bit holding device wherein the engagement member (12) comprises a steel ball (12).
An eighth aspect of this invention is based on the fifth aspect thereof, and provides a tool-bit holding device further comprising a rotatable operation grip (6) engaging the holder (10), wherein the holder (10) rotates as the operation grip (6) rotates.
A ninth aspect of this invention is based on the eighth aspect thereof, and provides a tool-bit holding device further comprising at least two grooves (14c, 14e) formed in the front cover (14), a second engagement member (8) supported on the operation grip (6) and being movable radially relative to the operation grip (6), the second engagement member (8) being fittable into one of the grooves (14c, 14e) in the front cover (14), and a second spring (9) for urging the second engagement member (8) toward the front cover (14).
A tenth aspect of this invention provides a tool-bit holding device in a percussion tool (an impact tool). The percussion tool includes a piston (25), a striker (21), an intermediate member (17), and means for causing the striker (21) to follow reciprocation of the piston (25) and to strike the intermediate member (17). The tool-bit holding device comprises a rotatable retainer sleeve (4) for accommodating a shank of a tool bit (1); a lock member (7) supported by the retainer sleeve (4) and being movable radially with respect to the retainer sleeve (4); means for engaging the lock member (7) with the shank of the tool bit (1) to limit axial movement of the tool bit (1); a fixed front cover (14) extending radially outward of the retainer sleeve (4); a plurality of grooves (4a) formed in the retainer sleeve (4); an engagement member (12) supported on the front cover (14) and being movable radially with respect to the retainer sleeve (4), the engagement member (12) being fittable into one of the grooves (4a) in the retainer sleeve (4); and a holder (10) rotatably provided on the front cover (14) and limiting radial movement of the engagement member (12) depending on a rotational position of the holder (10).
An eleventh aspect of this invention is based on the tenth aspect thereof, and provides a tool-bit holding device further comprising means (11) for urging the engagement member (12) toward the retainer sleeve (4), the spring (11) having a portion contacting the engagement member (12) and being radially movable, a small-diameter area (10a) formed by an inner surface of the holder (10) and being engageable with the portion of the spring (11) to inhibit radial movement of the portion of the spring (11) and radial movement of the engagement member (12), and a large-diameter area (10b) formed by the inner surface of the holder (10) for allowing radial movement of the portion of the spring (11) and radial movement of the engagement member (12).
A twelfth aspect of this invention is based on the eleventh aspect thereof, and provides a tool-bit holding device wherein the urging means (11) comprises a leaf spring (11) fitting around a portion of an outer circumferential surface of the front cover (14).
A thirteenth aspect of this invention is based on the twelfth aspect thereof, and provides a tool-bit holding device wherein the engagement member (12) comprises a steel ball (12).